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The Arthropods - PowerPoint

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					            The Arthropods

• Major characteristics of arthropods
  – Jointed appendages - Groups very often
     named in relation to number or type of
     feet.
  – Exoskeleton
  – Hemocoel
  – High degree of cephalization
               Arthropods
• Relative abundance.
  – 3/4 of all known species of animals are
    arthropods.
  – More known species of arthropods than known
    species of plants and animals combined. Great
    diversity in form and habitat.
   Major Groups of Arthropods
• Subphylum Trilobita - all forms extinct
  (believed) perhaps some of earliest
  arthropods
• Subphylum Chelicerata - First pair of
  appendages form chelicera or pincher-like
  structures used for feeding. 4 pair of
  walking legs, no antennae. The Arachnida
  is the only important parasitic group.
   Major Groups of Arthropods
• Subphylum Crustacea - mostly aquatic,
  most have gills, two pair of antennae.
  Biramous appendages, mandibles. Some
  are parasitic but we will not cover them.
• Subphylum Uriramia - Uriramous
  appendages, mandibles, one pair of
  antennae
   Major Groups of Arthropods
• Diplopoda - Millipedes - two pair of legs
  per body segment
• Chilopoda - Centipedes - one pair of legs
  per body segment
• Insecta - 3 pair of legs on adults, many with
  wings, most important group
 The arthropod serves as a direct
  cause of disease or discomfort
• Entomophobia (bees, spiders, tarantula,
  almost any bug)
• Annoyance ((biting flies, fleas, lice, ants or
  flies at a picnic, cockroaches)
• Accidental injury to sense organs (insect in
  eye, ear, swallow an insect
• Envenomization (bees and wasps, spiders,
  scorpions)
    The arthropod serves as a direct
     cause of disease or discomfort
•   Dermatosis (lice, mites)
•   Myiasis (infestation of fly larvae)
•   Allergy and related conditions (dust mites)
•   Blood loss from blood feeding insects
    (mosquitos, Fleas, etc)
      Arthropods Transmitting
             Parasites
• Arthropods as vectors or intermediate hosts
  – Mechanical carriers - serves to transport
    parasite
  – Obligatory vectors (some degree of
    development occurs with the parasite while it is
    in the arthropod) Often referred to as biological
    vector.
  – Intermediate host in some cases may be
    parathenic host
      Insect Mouth Parts and
     Transmission of Parasites
• Piercing-sucking - mosquito, tube structure
  penetrate skin and blood flows out the tube.
  Usually releases anticoagulating substance
  to prevent blood clotting.
• Cutting-sponging - sharp mandibles that
  break the skin and a labium that acts like a
  sponge. Important in transmission of
  organisms. Horsefly
      Insect Mouth Parts and
     Transmission of Parasites
• Sponging mouth type - Labium acts as a
  large sponge that absorbs liquids. Often
  regurgitates chemicals to breakdown the
  material. The housefly, Musca domestica is
  perhaps the most important insect to man
  because of its spread of disease
           Ways insects are
           beneficial to man
• Transfer of pollen in plants
• Useful products (honey, bees wax, silk)
• Major component of the food chain
• Biological control, decomposition of
  organic matter
• Beauty - butterflies
• Medicine - some used for medicinal
  purposes especially in Eastern medicine
  Insects of Parasitic Importance
• Anoplura (sucking lice)

• Hemiptera - the true bugs

• Siphonaptera - the fleas

• Diptera - the flies
                 The Lice
• Mallophaga (biting or chewing lice
  – 3,000 species
  – none of direct medical importance
  – common on birds and many mammals
• Anoplura (sucking
  – fewer than 500 species
  – some are of great medical importance
  – Only parasitize mammals
 Feeding methods of blood sucking
           Arthropods
• Solenophage (pipe + eating) type of feeding
  apparatus. Proboscis enters blood vessels
  and withdraws blood. (sucking lice and
  mosquito).
• In contrast, telmophage )pool + eating) is
  where mouth parts break the skin and blood
  and other tissue fluids form a pool which is
  then absorbed.
    Lice of Medical Importance
• Pediculus humanus (humanus) - Also called
  Pediculus humanus corporis the body louse
• Pediculus humanus capitis (Pediculus
  capitis) - the head louse
  – It is very difficult to distinguish the two
    morphologically although head lice are usually
    somewhat smaller
• Phthirus pubis the crab louse or pubic
  louse
   Pediculus humanus corporis

• Called grey backs, cooties, or a few other
  unrepeatable names.
• Live most of the time in the hosts clothing
  and come into direct contact with the host
  only for feeding.
• The eggs called nits and are cemented to
  fibers in the clothes. If clothes removed and
  not worn for several days, the nits will die.
   Pediculus humanus corporis

• Common in areas of high population,
  congestion, and poor sanitation.
• Importance as a parasite.
  –   Endemic or louse-borne typhus
  –   Trench Fever
  –   Relapsing fever - endemic relapsing fever.
  –   Pediculosis
 Endemic or louse-borne typhus
• Caused by bacterium, Rickettsia prowazekii
• Epidemics occur during times of crowding,
  poverty, poor sanitation.
• Often has high mortality
• Disease is transmitted when louse leaves
  infected host (because of the fever) and
  seeks out a new host. Rickettsial organisms
  passed out in feces and scratched into skin.
            Control of Lice

• Reduce crowding, proper sanitation, bathing
  and laundry of clothes and linens.
• Introduction of insecticides into clothing of
  persons under louse enhancing conditions.
• Many medications to kill or delouse a
  person
Pediculus humanus humanus
           Louse Life Cycle
• Nits on hair or in
  seams of clothing
• Three nymphal stages
• Adult lice
                    Lice
• Lice will leave person (and clothing ) if
  person dies or gets very high fever
• Travel to anther host relatively easily in
  crowded locations and in institutionalized
  conditions such as war, refugee camps, or
  times of war.
    Pediculus humanus capitis
• Head louse – mechanized dandruff
• Not know to transmit any pathogenic
  organism.
• Eggs or nits cemented to hair
• Often located on neck and behind ears
• Easily transmitted from one person to
  another and often occurs during school.
 Phthirus pubis – the crab louse or
            pubic louse
• Lives primarily in the pubic region but may
  be found in armpits or beard, eyebrows, or
  eyelashes.
• Does not transmit any known pathogens.
• Often transmitted during sexual activity.
Lice Nits

				
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